Luminescent properties of BaCl₂ under VUV excitation

We observed the luminescence and excitation spectra of a BaCl₂ single crystal, which is a promising fast scintillating material, under the UV-VUV excitation. A prominent band was observed at 410 nm under the excitation of almost the entire range of wavelengths region investigated, and it was revealed that this band is extrinsic, because this band was excited with sub-band-gap radiation. A dramatic increase in the intensity of this band was observed at wavelengths less than 90 nm, which was a manifestation of electron excitation multiplication. In addition, we observed a band at 310 nm under the excitation of only 170-190 nm, and this band was possibly a result of self-trapped excitons. The observation of these two bands was quite similar to the scintillation spectra obtained under X-ray or high-energy proton irradiation in previous reports. The knowledge of these luminescence origins are highly important from the viewpoint of the improvement in the scintillation properties of BaCl₂ and its application to scintillating materials operative at a high counting rate.